1. Field of the Invention
This invention relates to apparatus for compressing particulate matter and, more particularly, to apparatus for compressing particulate matter with heat and compressive force.
2. Description of the Prior Art
Prior art compacting machines generally embody either an extrusion screw apparatus or a ram compression apparatus for compressing or compacting particulate matter. In the extrusion screw apparatus, particulate matter is forced by a screw auger through a forming die and into a tube. Because of the friction in the tube, considerable back pressure is developed at the end of the screw, causing bonding of the particulate matter. Such machines have the advantage that air and excess moisture have a channel for escaping along the screw, and they have a further advantage in that the particulate material is well mixed and evenly distributed throughout the length of the product being formed.
Machines using the extrusion screw concept also have disadvantages in that the tube is susceptible of plugging, which generally results in substantial down time for the machine. Moreover, the center of the product formed is often hollow or is less dense than the exterior of the product, since the particulate matter under pressure at the end of the screw flows radially to fill the space left by the core of the screw, after, or as, the screw is retracted.
Another disadvantage of the extrusion screw concept is the susceptibility of severe wear of the extrusion tube and screw if abrasive material, such as coal, bark, or other residue containing dirt, and the like, is introduced into the machine.
In the ram compression apparatus, a charge of particulate material is placed in a compression chamber, and a ram presses the material into a cylindrical product, such as a log. Such apparatus is advantageous in that it provides a very high compacting force, and it is not easily plugged. However, it also has a disadvantage in that air and excess moisture can be trapped in the compression chamber as the product is being formed. Moreover, in order to achieve the necessary production scheduling to make the process cost efficient, the product cannot be maintained at a relatively high compacting pressure for more than a relatively short period of time.
U.S. Pat. No. 2,833,633 discloses apparatus for forming particulate matter, such as saw dust, into logs. Particulate matter is fed into a relatively long tube and is compressed as it flows through the tube. Within the tube, the compressed material forms a continuous log which is broken off in predetermined lengths, if desired, at the discharge end of the tube. The tube is fed from a hopper, and a piston or ram is used to compress the material in the tube.
U.S. Pat. No. 3,232,722 discloses apparatus for producing logs from particulate matter, such as saw dust, wood chips, and the like. A screw auger is used to feed the particulate matter into a cylindrical sleeve. This first sleeve includes a plurality of axially extending keys to prevent the particulate matter from rotating with the screw and to keep the particulate matter from moving longitudinally in the sleeve. From the sleeve, the particulate material flows through a second sleeve and into an extrusion die where compaction takes place. The diameter of the second sleeve tapers from that of the first sleeve about the screw auger to the minimum diameter of the extrusion die.
U.S. Pat. No. 3,240,573 discloses apparatus for manufacturing a log from sawdust mixed with a filler or extender, wax, and a binder. A screw auger is used to convey the sawdust, with its ingredients mixed together, directly to a bag in which the mixture will be packaged. Compaction occurs within the bag.
U.S. Pat. No. 3,427,960 discloses apparatus for compacting material, such as sawdust and binder, into cylindrical blocks. A rotating drum having at least three compression chambers, open at both ends, is used for forming the cylindrical blocks. The chambers in the rotating drum are successively aligned with a feeding position, a compression position, and a discharge position. Material is first fed into a chamber, and is then compressed within the chamber, and eventually the material is discharged from the chamber.
U.S. Pat. No. 3,506,415 discloses apparatus for producing cylindrical logs by compressing particulate material and a binder. An auger screw is used to advance the material through a cylinder or barrel where the material is compacted and formed.